How Biomethane is Produced

Biogas Tools

In contrary to fossil fuel derived methane which is simply pumped from the ground, biomethane is produced from “fresh” organic matter in landfills or biogas plants. Both methods base on anaerobic digestion which is performed by the anaerobic microbes that thrive in absence of oxygen. These microbes, however, do not produce pure methane. They also produce carbon dioxide and some other gases which is why biogas typically requires treatment known as scrubbing to make it useful as fuel.

Although biogas plants produce carbon dioxide and some other greenhouse gases, they do not contribute to the greenhouse effect. On the contrary, they help reduce the emissions of carbon dioxide and other gases which warm up the Earth’s atmosphere. Firstly, biomethane production prevents release of methane which is one of the most potent greenhouse gases, secondly it reduces the amounts of a number of greenhouse gases that are released into the atmosphere when organic matter is left to decompose naturally, thirdly it reduces the need for fossil fuel burning which is the number one cause of global warming and lastly, it reduces the need for firewood and helps save the forests which remove considerable amounts of carbon dioxide and other air pollutants.

Production of biomethane by biogas plants basically follows the natural process of methane production. Biogas plants collect various types of organic matter and store it in air-tight tanks to create ideal conditions for the anaerobic microbes that produce gas during digestion. Biogas which mostly consists of methane and carbon dioxide is then stored on the top of the digester tank or is extracted to the nearby gas holders. This can help reduce emissions from cars depending on the production processes and the type of organic matter used, biogas may require treatment to remove toxic gases such as hydrogen sulfide and volatile siloxanes. Most modern biogas plants also use purification processes that reduce the carbon dioxide content.

Biogas Production

In addition to producing biomethane, many biogas plants use it on site to produce electricity or heat. Farm-based biogas plants for instance use the produced biomethane to cover their own energy needs but they may also sell surplus of electricity to the grid or suppliers. Off farm-based biogas plants produce biomethane for the market either by generating electricity/heat themselves or selling biomethane in a compressed form to the gas mains.

Another way to produce biomethane is to capture the gas in landfills. Methane in landfills is produced when the organic matter is covered and compressed with the material from above preventing oxygen from reaching the organic material. This creates anaerobic digestion and production of methane which can be captured on site. However, biomethane production in landfills is problematic because methane is explosive in contact with oxygen and because it is difficult to capture it completely. And since methane is as much as 20 times as potent greenhouse gas as carbon dioxide, production of biomethane in landfills may contribute to global warming. In addition, landfill gas also contains a number of other gases which either pollute the air or increase the greenhouse effect, or both.